4G vs. 5G

Using more spectrum and advanced antennas, vendors and operators plan to increase 4G mobile speeds. But the key to increasing speeds as researchers look at future networks, which will someday be dubbed 5G by marketers, is to shorten the distance between users and base stations, and allowing them to automatically be reconfigured.

Historically, a new mobile generation has included two basic components, a mobile standard and spectrum allocation, according to Håkan Djuphamma , vice president of architecture and portfolio at Ericsson.

Because LTE is at the limit of what is physically possible it now makes less sense to develop another standard from the ground up, Djuphammar says. Also, the allocation of spectrum has become increasingly fragmented, because the airwaves are so crowded.

That said, networks will still continue to evolve going forward, according to Djuphammar. But, at the moment, the industry isn't working towards a big 5G launch.

The development of so-called het nets, or heterogeneous networks, which use a mixture of traditional large base stations and smaller cells, placed in areas where there are a lot of users, will be key to how mobile networks evolve, according to Djuphammar.

The basic idea is the same as with today's femtocells, which are most often placed in homes to offload the rest of the network, while also improving coverage and providing better capacity for subscribers connected to it. But in a het net, the smaller base stations would be more integrated with the rest of the network.

It's about building network structures that would allow devices with 2G, 3G, 4G and in most cases Wi-Fi, as well, to jump between different forms of access depending on the load in the different parts of the network and the application currently used, and can dynamically manage device access in an intelligent way, according to Djuphammar. Doing all that is a pretty challenging task, he says.

The same spectrum bands will also be used for different mobile standards. Depending on what kind of devices are connected to a base station it will be able to change the amount of spectrum used to maximize performance in real-time.

"Today we have a static allocation of spectrum, but in the future it will be completely dynamic. For example, if there are no phones in a cell that need to use GSM the entire spectrum can be used for 4G. But when a GSM phone comes back into the cell, the base station again reconfigures its spectrum allocation," Djuphammar says.

At the KTH Royal Institute of Technology they have started to examine what networks could look like by 2020, which is when 5G would arrive if the telecom industry continued to launch a new network generation every 10 years.

The aim is a thousand fold capacity increase, according to Jens Zander, a professor in Radio Communications at the university and head of its center for wireless systems Wireless@KTH, who is also a big proponent of denser mobile networks where the distance between base stations is much shorter.

"Beyond LTE, I think the most important thing is finding good and cheap solutions over short distances, and have base stations that are as easy to install as Wi-Fi, but have much higher capacity and have better coordination with the rest of network," Zander says.

An import part of simplifying the installation process is the concept of self-organizing networks, which allow operators or end-users to connect a base station to the network and it would automatically be installed.

"A big part of the cost for current networks is that they have to be carefully planned," Zander says.

Short-term improvements will include the use of more spectrum and multiple antennas. Continuous spectrum is a limited resource, so vendors came up with carrier aggregation. The technology allows operators to bunch together spectrum in different bands and use them as one data link.

Another way to increase capacity, which is already used today, is MIMO antenna technology, which uses multiple antennas in the base station and on the device to increase speeds.

The big challenge with MIMO is to fit all the needed antennas on the user device; and more antennas mean more capacity.

It is very difficult to fit more than two antennas in a mobile phone, according to Zander. For MIMO to work, the antennas need to see a slightly different version of the radio signal, which the distance between the antennas allow them to do.

How long the distance needs to be depends on the frequency used to send the data.

The growing size of many high-end smartphones, thanks to the fact that vendors are including bigger screens, will help. Also, because of their larger size, it will be easier to include many antennas on tablets and laptop.

Today, MIMO is only used to increase download speeds, but it will likely be added to upload traffic, as well.

So going forward the development of mobile networks will be more evolutionary that revolutionary.

"Maybe something will come along that the industry feels is such a big change or addition to 4G that it could be labeled 5G," Djuphammar says.

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